High frequency tube



Dec. 21, 1943. R. s. BRIGGS I 7 2,337,444

HIGH FREQUENCY TUBE I Filed Feb. 15, 1942- 2 Sheets-Sheet l ATTORNEYS R. s. BRI GGS HIGH FREQUENCY TUBE Filed Feb. 13, 1942 2 Shets-Sheet 2 INVEN'ILOR m4; ATTORNEYS Patented Dec. 21, 1943 UNITED STATES PATENT OFFICE HIGH FREQUENCY TUBE Richard S. Briggs, Beverly, Mass, assignor to 8 Claims.

This invention relates to a tube for use with socalled ultra-high frequency.

In the use of ultra-high frequency tubes in radio work it becomes highly important to shorten the lead of the elements from within the tube to their connection outside of the tube in order that the radio frequency transmission may be over as short a path as possible. In tubes already in use designed for this high frequency work leads are taken out through the walls of the envelope closest to the plate and grid in order to shorten these leads but in most instances the leads from the filaments or cathode filaments extend out through the stem or press and present a problem in shortening the leads for this element. To lead the filaments out through the side of the glass envelope, while the same may have been proposed, presents an expensive seal,

especially when a plurality of conductors are used for this purpose, and is undesirable from the standpoint of practicability in the construction cost of a tube.

1 One of the objects of this invention is to leave the filament conductors in the stem press in a.

manner heretofore provided but to, in effect, nullify their high frequency carrying capacity by short-circuiting this high frequency current from a point just below the heating portion of the filament which is utilized.

Another object of this invention is to shortcircuit the high frequency current through the glass of the tube envelope while leaving the envelope and the stem press with its filament lead therein in the customary manner found to be economical in manufacture.

-, Another object of the invention is to provide a high frequency path of low resistance for transmitting high frequency current out of the tube through the wall thereof to the ground rather than along the filament wires.

Another object of the invention is to utilize a capacity coupling which will conduct the high .frequency current and provide less resistance :where high frequencies are used than in a single or double lead wire from the filament.

Another object of the invention is to provide an arrangement which may be utilized with various forms of filaments or with various forms of plate and grid arrangement or numbers of plate and grid arrangements forming a plurality of other elements in the tube.

Another object of the invention is to provide a -construction which may be utilized advantageously with a shield for thetube by afiording vention consists of certain novel features of con struction, as will be more fully described and particularly pointed out in the appended claims.

In the accompanying drawings:

The figures are largely diagrammatic,

Fig. 1 illustrating in section the envelope, stem press and parts contained within the envelope of my tube.

Fig. 2 is a similar view to Fig. 1, illustrating a slightly modified arrangement.

Fig. 3 is a section on line 3-3 of Fig. 2.

Fig. 4 is a view similar to Fig. 1 but showing a still different modification than shown in Fig. 2.

Fig. 5 is a View illustratiing the arrangement shown in Fig. 1 but showing a slightly modified arrangement in the provision of a portion shown in Fig. 1 extended to provide a base.

Fig. 6 is a sectional View illustrating a still different modification and development which this invention is capable of.

In proceeding with this invention I have devoted attention primarily to the shortening of the lead over which the high frequency current from the filament is transmitted, and in accomplishing this I have utilized a capacitance with one of its plates attached to the filament within the tube and the other plate attached to an eX- ternal circuit without the tube, the spacing being such that the glass envelope is substantially equally distant from both plates. The condenser is in the form of concentric cylinders and provides a large number of paths radially outwardly from .the filament for the transmission of high frequency current along a path of very low inductive reactance from about the filament so that in effect a very short lead for the high frequency current from the filament is provided, and a short circuit is provided from the filament to the ground via the very low capacitative reactance of the condenser, rather than along the filament leads which are used for heating the filament. The capacitative coupling obtained by the aforesaid manner is used as a low impedance cathode lead for the express purpose of carrying an ultrahigh radio frequency cathode current. The filament'or heater connections to the cathode are merely used to supply direct current or low frequency alternating current power to the cathode.

' These leads may have suitable chokes interposed manner radio frequency cathode currents are effectively by-passed and need not travel through the filament or heater lead wires which may offer considerable impedance at ultra-high radio frequencies.

Although the drawings show application of the cathode shield to vacuum tube triodes, the use of the same may be generally applied to multielement tubes where a common cathode lead is used. In the case of pentodes, it may be advantageous to connect the suppressor grid directly to the cathode shield, the latter serving a dual purpose by combining suppressor grid and cathode leads. The following is a more detailed description of .the arrangement by which I accomplish this desired result.

I have illustrated in Figs. 1, 2, 3 and 4 merely the envelope and pres portion without showing the base and studs usually mounted on the envelope, to which the leads are connected, while in Figs. 5 and 6 the base is shown with a certain modified concentric tube lead arrangement in the latter figure. In all these various figures the. same numerals will be used in referring to the same or equivalent parts of the tube while the modifications will be pointed out with different reference numerals for the sake of descriptive clarity. 7

In the various figures the glass envelope or bulb It] is sealed to the .stem press II. at substantially the location l2, at the lower, portion of the envelope in a well known manner. An exhaust conduit I3 is sealed ofi as at l4 after the envelope has been exhausted. Support Wires I5 and iii are molded into the stem press II and extend upwardly into the envelope and, through means of insulating spacers l1 and I8, mount a plate 20 and a grid 2!. The plate 20 is connected by means of tab 22 to a top terminal 23 extending through and sealed in the top wall of the envelope while the grid is connected by the tab 24 to the terminal 25, also extendin through the top wall of .the envelope as illustrated. The plate and grid may be inpunted within the envelope by any suitable means, that shown being one conventional form which may be utilized, it being understood that the particular form of plate and grid mounting are not a part of this invention.

. Within the envelope I have provided 'an inverted cuplike shield designated generally 26 and which consists of a cylindrical portion 21 located close to the glass envelope I0 and an end wall 28 which is attached to the support wires 15 and 16 at 29 and 3!] whereby the cup. is supported in desired position within the envelope.

A mica spacing ring 21a may be positioned be- .tween the cylinder2l and the glass envelope.

A center metallic filament support 3| extends upwardly from the midpoint of the bottom wall 28 and passes throughthe spacers l8 and I1, and .in firm frictional engagement therewith, to be supported thereby. The cathode filament 34 is attached as at 3.5. to the upper portion of this support 3| and extends downwardly in opposite helical paths spaced from the supportBl and passing through theopenings 3B and 31 in the insulating spacer l8 and then through the openings Stand 39 in the bottom wall 28, but out of contact therewith. The filament lead then continues through the press as at 40-41 toan .external source for the application of heating power. In this manner. the cathode filament is connected to the end wall 28 of the inner shield 26 through thecenter. supportpost. i 7

I have arranged a metal cylindrical member 42 outside of the envelope l0 and spaced from the envelope by an insulating spacer 43 and filling material such a mica so that the envelope l0 will be substantially midway between the cylindrical member 42 and the cylindrical portion 21 of the shield 25. The member 42 will have an axial extent at least as great as the axial extent of the cylindrical portion 21 of the shield 26. These spaced cylindrical surfaces provide a condenser or capacitance which is electrically connected to the cathode filament 34 at a location at the center of its heating portion .35, via Supporting rod 3!. This capacitance serves as a low impedance short circuit for the high frequency current from the cathode filament to an external circuit through the wall l0 of the envelope. By reason of the cylindrical or circular arrangement of the plate of the condenser, a large or infinite number of paths for transmission of this high frequency current from the tube is provided. Thus low impedance is had and the efiect of the short lead from the cathode is provided, the capacitative reactance in ohms being known to be in accordance with the equation 21rfc where j equals frequency in cycles per second and 0 equals capacity in farads.

Various arrangements of this capacitance which I have just described may b provided, and in Fig. 2 instead of providing an inner cylindrical shield designated 26 in Fig. l I have provided a divided inverted cup now designated in two parts 46 and 41, there being a substantially semi-cylindrical wall 48-49 with. an end 50 for the semi-cylindrical part 48 and an end 5| for the semi-cylindrical. part 49. These are each independently supported on support wires [5 and I6 as at 52 and 53 while the support wires extend completely through the stem press, their extensions being designated l5a and lBa. The filament support 54 is molded into the stem press II and extends upwardly in the space between the two halves of the shield. The cathode filament 34 is supported as at 3 5 'onthis support 54 and extends about it in opposite helical coils and in spaced relationrand is connected to the bottom Wall as at 55 and connected to the end wall 5i as at 56. The outer cylindrical wall 42 is the same as heretofore described in connection with Fig. 1. I

. In the use of the construction shown in Figs. 2 and 3, energy is supplied to the filament for heating it and for electron emission through the leads I 5a and Ilia, while the filament is connected to the capacitance 43, 49, 42' and will conduct the high frequency current from the cathode filament to some external circuit.

In the showing in Fig. 4 the cathode shield 26 is as shown in Fig. 1 except there is provided a central opening in the end wall 28 through which there extendsa heating filament 61 in generally U-shaped formation withv its ends 62 and 63 connected to the leads 6.4 and 65 extending through the stem press. A cathodesleeve 66 surrounds theheating filament 6| and is, insulated therefrom. Thebottom of thiscathode sleeve is electrically connected to. the bottom wall 28 by one or more tabs..6l:, and the support 16 may conduct. direct. current or. low. frequency alternatingrcurrent to the cathode for its. emissionof electrons.

In the various showings which I have above described, any base may be utilized, but it is often convenient to utilize the outer cylindrical member as a base and I have shown at 68 in Fig. this cylindrical member as extending downwardly a sumcient extent to provide a base while a wafer 69 is held in a recess and in turn supports the contact pins H and 12 to which the leads from the stem are connected.

In Fig. 6 I have carried this outer cylindrical member now designated 13, upwardly and, through some insulating spacing part 14, have mounted a concentric tube 15 which may form one of the leads of a shielded arrangement. In this case I have connected the plate to the inner concentric member 15 by means of the connection 16 while the grid lead 11 may extend through an opening 18 in the outer tube for a short lead to the circuit in which it is located.

I claim:

1. A radio frequency tube comprising a. dielectric envelope enclosing electrodes one of which is a cathode element, heating current leads connected to said element and providing a continuous metallic circuit only for said cathode element, cylindrical inner and outer metallic members on either side of said envelope providing an electrical capacitance, means connecting the inner member to said cathode element whereby the outer member may be connected to an external circuit to conduct ultra high frequency current from said element through the dielectric envelope.

2. A radio frequency tube comprising a dielectric envelope enclosing electrodes one of which is a cathode element, a continuous metallic circuit for conducting heating current to said element and constituting the only lead in means for said element, inner and outer cylindrical metallic members on either side of said envelope providing an electrical capacitance, means connecting the inner member to said cathode element whereby the outer member may be connected to an external circuit to conduct ultra high frequency current from said element through the dielectric envelope, one of said members being interposed in the heating current circuit.

3. A radio frequency tube comprising a dielectric envelope, a cathode element therein, heating current leads connected to said element, inner and outer cylindrical metallic members on either side of said envelope providing an electrical capacitance, means connecting the inner member to said cathode element whereby the outer member may be connected to an external circuit to conduct radio frequency current from said element through the dielectric envelope, said outer member comprising the base for the tube.

4. A radio frequency tube comprising a dielectric envelope, a cathode element therein, heating current leads connected to said element, inner and outer cylindrical metallic members on either side of said envelope providing an eleceither side of said envelope providing an electrical capacitance, means connecting the inner member to said cathode element whereby the outer member may be connected to an external circuit to conduct radio frequency current from said element through the dielectric envelope, said outer member extending along the tube longitudinally thereof and an inner concentric line conductor connected with said outer member.

6. A radio frequency tube comprising a dielectric envelope, a cathode element therein, heating current leads connected to said element, inner and outer cylindrical metallic members on either side of said envelope providing an electrical capacitance, means connecting the inner member to said cathode element whereby the outer member may be connected to an external circuit to conduct radio frequency current from said element through the dielectric envelope, said outer member extending along the tube longitudinally thereof and an inner concentric line conductor connected with said outer member and another of the elements of the tube being connected to said inner concentric line conductor.

'7. A radio frequency tube comprising a dielectric envelope enclosing electrodes one of which is a cylindrical metallic member on the inner side of said envelope and a cylindrical metallic member on the outer side of said envelope providing an electric capacitance, a metallic wall extending inwardly from the inner of said members, a cathode element connected to and supported by said wall, said outer member being adapted to be connected to an external circuit to conduct an ultra high frequency current from said element through the dielectric envelope.

8. A radio frequency tube comprising a dielectric envelope enclosing electrodes one of which is a cylindrical metallic member on the inner side of said envelope and a cylindrical metallic member on the outer side of said envelope providing an electrical capacitance, a metallic wall extending inwardly from the inner of said members, a cathode element connected to and supported by said wall, said outer member being adapted to be connected to an external circuit to conduct an ultra high frequency current from said element through the dielectric envelope and continuous metal heating current leads extending from said element.

RICHARD S. BRIGGS. 

